In order to maintain high pressure-resisting quality in using a SiC MOSFET as a power device, it is required to increase threshold voltage to some extent. In addition, at the same time, in order to realize low on-state resistance, it is required to increase channel mobility of a MOSFET (decrease channel resistance).
JP-A-2008-270258 (PTL1) discloses a method for shifting the threshold voltage of a Si trench type MOSFET to a desired value by forming a gate insulation film or a floating gate which are formed on a Si oxide film/Si nitride film/Si oxide film (ONO film) in a Si trench and by injecting a carrier into the ONO film or the floating gate. Furthermore, as a method for injecting an electric charge, a method for injecting an electron by injecting an FN electron from a Si substrate side, and a method for applying pressure between a drain and a source and injecting the electric charge by avalanche breakdown, are disclosed.